Boeing has disclosed commitments by two unnamed customers for a total 15 787-9s.
The US manufacturer says that one of the two carriers is an existing 787 operator, while the other is a new customer for the long-haul twinjet.
It adds the deals have a total list-price value of $4.2 billion, but have yet to be finalised.
No engine selection has been disclosed.
The 787 is available with GE Aviation GEnx or alternatively Rolls-Royce Trent 1000 engines.
Boeing says it secured nearly 100 net orders for the 787 in 2018 and foresees additional commitments that will be finalised in coming months.